Our recent studies have focussed on the processes underlying granule assembly, synthesis and insertion of catecholamines into granules, movement of granules to sites of secretion and membrane contact and fusion between granules and plasma membranes leading to exocytosis in chromaffin cells. Some work has also been done with Islets of Langerhans. Our work this year has included the synthesis and packaging of vasoactive intestinal peptide, as well as synthesis of norepinephrine from transported dopamine within the granule. Ascorbic acid seems to act on the enzyme dopamine-Beta-hydroxylase from outside the granule. A mystery concerning how catecholamines can be synthesized in such quantity in chromaffin cells, in the face of massive monoamine oxidase activity has been solved. The MAO in chromaffin cells is type B, with low affinity for Beta-hydroylated catecholamines. The membrane contact and fusion event, thought to be involved with calcium and synexin, is now more fully understood, by both fast freezing fixation and electron microscopy, as well as by monodonal antibodies directed against synexin. The pharmacology of insulin secretion from Islets of Langerhans also seems to follow the pharmacology of synexin, not calmodulin as hitherto thought. Finally, we were able to isolate the neuroendocrine barrier of the adrenal medulla, the endothelial cells making up the capillary network supporting the endocrine chromaffin cells. These cells were found to form true capillaries in vitro, and constitute an exciting new thrust forward in our attempts to understand adrenal gland endocrinology.